Prominent Turkish journalist Ahmet Sik was detained on suspicion of spreading terrorist propaganda, state media and an opposition lawmaker who spoke to the reporter said.
Sik works for the daily Cumhuriyet, one of the few dailies still critical of the government as Turkish authorities have purged tens of thousands, largely from the state apparatus, in the wake of a coup attempt last July.
Prosecutors could not be reached for comment but Sik himself tweeted that he was being taken to the prosecutor's office.
The state-run Anadolu news agency said Sik was accused of spreading terrorist propaganda and insulting the state, the judiciary, the military and the police through several tweets and his work on Cumhuriyet.
Anadolu cited more than half a dozen tweets. Most were about the state's fight against Kurdistan Workers' Party (PKK) rebels, while one was about this month's killing of the Russian ambassador in Ankara.
Most were about the state's fight against Kurdistan Workers' Party (PKK) rebels, while one was about this month's killing of the Russian ambassador in Ankara
Baris Yarkadas, a lawmaker for the main opposition Republican People's Party (CHP), tweeted that Sik had told him he was being accused of spreading terrorist propaganda.
Separately, a court in Istanbul ordered the release, pending trial, of award-winning novelist Asli Erdogan and linguist Necmiye Alpay, Alpay's lawyer said. The two had been in jail since August on charges of belonging to a terrorist organisation and harming national unity.
They are among a total of nine defendants who worked for a pro-Kurdish newspaper closed by authorities, some of whom face possible life sentences.
Alpay and Erdogan, who is not related to the Turkish president, both pleaded 'not guilty'.
Journalists in jail
The PKK, which has been fighting for three decades for autonomy for Turkey's mainly Kurdish southeast, is considered a terrorist group by the European Union and the United States as well as Turkey.
At least 81 journalists are imprisoned in Turkey, according to the New York-based Committee to Protect Journalists (CPJ), and more than 130 media outlets have been shut since July. Most of the detained journalists and writers are accused of spreading terrorist propaganda.
Over 110,000 civil servants, police, academics and others have been detained, suspended or dismissed over suspected links to Fethullah Gulen, a U.S.-based cleric accused by Ankara of orchestrating the coup. Around 40,000 have been formally arrested.
The scale of the crackdown has alarmed Turkey's Western allies and foreign investors, but Ankara says it is justified by the threat posed by Gulen's network, which it says is a terrorist organisation. Gulen, who lives in the United States, denies the charges.
Sik himself is a long-standing critic of Gulen. In 2011 he was jailed for a year over a biography of the cleric, one of hundreds of imprisoned soldiers and journalists who said they had been the victims of Gulenist judges and prosecutors. The convictions were later overturned and the cases thrown out.